Broach



Feb.14,1967

Original Filed Oct. 2. 1961 C. O. LOFGREN ETAL BROACH 4 Sheets-Sheet 1 gaat] 4 Sheets-Sheet 2 BROACH C. O. LOFGREN ETAL Feb. 14, 1967v Original Filed Oct. 2 1961 BROACH original Filed oct. 2, 1951y 4 Sheets-Sheet 3 Feb. 14, 1967 c. o. Lor-GREN ETAL y 3,303,552

BROACH v original Filed oet. a, 1961v 4 sheets-sheet 4 United States Patent O 3,303,552 BROACH Charles 0. Lofgren and Axel Anderson, Rockford, Iii., assignors to Sandstrand Qorporation, a corporation of Illinois Original application Get. 2, 196i, Ser. No. I42,t8, now Patent No. 3,222,702. Divided and this applica-tira Mar. 3, 1965, Ser. No. 437,382

6 Claims, (Cl. Ztl-$5.1)

This application is a division of application Serial No. 142,088, filed October 2, 1961, and now Patent No. 3,222,702.

This invention relates to a breaching structure and more particularly to a broach.

An obiect of this invention is to provide a new and improved broach.

A further object of the invention is to provide a new and improved broach having an integral blade body in which the cutting teeth define a curved cutting profile with the teeth arranged on the body of the broac'n and shaped to have the tooth form and location maintained identical relative to the broach holder locating surfaces during repeated sharpenings.

Another object of the invention is to provide a breach as defined in the preceding paragraph in which the blade body has a rear edge and connecting side edge arranged at an acute angle with the side edge being generally parallel to a face of a cutting tooth on said body.

Further objects and adavntages will become apparent v from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a front elecational View of the rotary broaching machine;

FIGURE 2 is a plan view of the work holder structure shown in FIGURE l;

FIGURE 3 is a view similar to FIGURE 2 on an enlarged scale;

` FIGURE 4 is a fragmentary front elevational view of the broach holders shown in FIGURE 1;

FIGURE 5 is a section through a part of t-he broach holder and taken generally along line 5-5 in FIGURE 4;

FIGURE 6 is a fragmentary section taken generally along the line 6--6 in FIGURE 4;

FIGURE 7 is a fragmentary section taken along the lines 7-7 in FIGURE 4;

FIGURE 8 is a section taken along the line 8 8 in FIGURE 9;

FIGURE 9 is a plan view of the adjust-ment mechanisrn shown at the upper end of FIGURE 7;

FIGURE 10 is a fragmenary side elevational view of the work holding fixture shown in FIGURE 1;

FIGURE ll is a central vertical section of the drive for work holding fixture shown on an enlarged scale;

FIGURE l2 is a detail plan view of the blade-shaped broach;

FIGURE 13 is an end elevational view of the broach looking toward the edge having the cutting teeth; and

FIGURE 14 is an enlarged fragmentary view of a portion of the cutting edge of the broach.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail an embodiment of the the invention with the understanding that the presentl disclosure is to be considered as an exemplication of the principles of the invention and is not intended to limiti the invention to the embodiment illustrated. The scope ofthe invention will be pointel out in the appended claims.

As shown generally in FIGURES l, 2 and 3, the rotary broaching machine embodies a head supported on a suitable base (not shown). The head carries a rotatable work holding device 21 which rotates on an axis 22 for ICC carrying workpieces such as screw blanks sequentially past a first broaching station, indicated generally at 23, and a second breaching station, indicated generally at 24, with the rotation of the device 21 being shown by the arrow 25. The work holding device 21 is generally in the form of a drum having about its periphery a continuous series of individual work holders or fixtures, some of `which are shown at 26, 27 and 28 in FIGURES 2 and 3, which receive screw blanks from a supply having a supply chute 3f.' and are placed in the holders by a feed wheel 3l. By rotaion of the feed whel 31, the screw blank is delivered to one of the work holders and is clamped therein with rotation of the working holding device 21 carrying the screw blank with the head exposed out on the periphery of the device through the two broach stations. The workpiece is subsequently released from the work holding device 21 for movement into a chute 32 which leads the screw blank with-the head slotted to a storage container. Immediately `preceding the chute 32 a driven deburring tool may be `mounted to remove any `burr obtained from formation of the slot in the screw head.

The work holding fixture 21 and the mechanism associated therewith are shown in FIGURES l, 2, 3 and 10. The drum 21 is driven from a suitable source of power, such as an electric motor, driving a Worrn 35 (FIGURE 1l) which drives a Worm wheel 36 fixed to a shaft 37 coaxial with axis 22 and rotatably mounted in spaced bearings 38 and 39 in the head, and which has the drum 21 secured thereto.

Each of the individual work holders is of the same construction and embodies a first member 4t) secured to the drum and having a V-shaped notch 41 facing generally in the direction of travel of the drum for receiving a workpiece 42, as shown in FIGURE 3. A second member 43 is movably mounted relative to the first member 49 and is slidably guided by suitable undercuts formed in the next adjacent work 'holder member 40 and the associated work holder member 40. The second member 43 has a sloped surface 44 tapering toward an exposed end 45 whereby as the second member 43 moves from the retracted position shown for the holder 26 in FIGURE 3 to the extended position shown in connection with holder 28 in FIGURE 3, t-he sloped surface progressively moves toward the notch 41 while the member 43 is actually moving lengthwise. With the construction of the V-shaped notch as well as the sloped surface 44 on the second member 43, the work holder is capable of holding screw blanks of varying diameters whereby different size blanks can be handled wit-hout any change in the set-up of the machine. The second member 43 of the work holder is yieldably urged to its extended position by a spring 46 connected between the member, as indicated at 47, and the drum, as indicated at 48. The work holder member 43 is maint-ained in a position to receive a workpiece by means of a stationary cam 50 located to the rear ofthe drum 21 and which terminates at 51, whereby a follower roller 52 on the member 43 moves off the cam to permit the spring 46 to function to extend the member to clamp a workpiece. The workpiece is held in clamped position as it passes the broaching stations 23 and 24 and when the workpiece reaches the chute 32 the cam again becomes effective with a lead-in end 53 as shown in FIGURE l0 being positioned to engage the follower roller 52 of the movable work holder member. The cam 50 is suitably secured to the frame of the machine by an attachment bracket such as indicated at 54.

There are two detection controls associated with the workpiece and the work holder, with the first of these detecting that the screw blank is properly located heightwise in the work holder. If the blank is located too high this could result in damage to the broaches. This detecescasez tion is obtained by a pivoted member 55 located to be engaged by a screw located in a work holder and backed up -by spring-loaded plunger S6 which is mounted for vertical movement as viewed in FIGURE 1. If a screw blank is located too high in the holder the member 55 is pivoted clockwise about a pivot 57 as viewed in FIG- URE l, to raise the plunger 56 and operate a switch 58 which is connected into the circuit for the drive motor for the machine and which, when operated, stops the motor and operates an indicator light. The sec-ond detection control obtained is to determine if a work-piece is properly clamped in the holder. This construction is shown in FIGURE 3 and embodies a member 60 pivoted at 61 and urged toward the work holders by a plunger 62 which is spring-loaded by a spring 63 engaged therewith. As will be seen in FIGURE 3, the member 60 has a first sloped surface 64 and a second sloped surface 65 which, because of the spring loading, delivers a hammer blow to the movable member 43 `of the Work holder to insure a tight clamped relation with a workpiece. When a movable mem-ber is given the hammer blow, the hammer member 60 is in effect driven back, and if the movable member has not moved to clamping position, the hammer member 60 will be driven back too far and the plunger 62 Willrindicate this position and operate the switch 66 to operate an indicator light which indicates to an operator that a part is not properly clamped and to stop the machine.

Means are associated with the camming device 21 for placing individual workpieces in the individual work holders and as shown this means comprises the feed wheel 31 which is in the form of a disc having a plurality of notches 67 about its periphery each of which can receive an individual screw blank and hold the blank therein whereby as the feed wheel rotates a screw blank in a notch 67 is delivered into a notch 41 of a work hol-der. Because the screw blank is headed it will seat itse-lf and hold itself within the notches 67V to a work holder notch 41 which is accomplished Linder the urging of a Flexible spring member 68 as assisted by centrifugal force imparted to the workpiece during the rotation of the feed wheel.

Means are provided for driving the feed wheel 31 in timed relation to the Work holding drum 21 in order that the feed wheel notches 67 will present themselves in timed relation to the individual work holders. Thismeans comprises a gear 70 rotatable with the drum 21 which meshes with a gear 71 xed to the shaft 72 to which the feed wheel 31 is loosely mounted. The feed wheel is driven from the shaft 72 by a clutch mechanism embodying a member 7 3 pinned to the `shaft and having la series of pins 74 which are spring loaded upwardly into engagement with the underside of the feed wheel 31 by a spring 75 and engage in recesses on the underside of the feed wheel. 1f a jam occurs in the feed wheel resulting in'inability of the feed wheel to rotate, the clutch pins 74 move out of the recesses on the underside of the feed wheel against the urging of the spring 75 to disengage the drive to the feed wheel. This disengagement results in operation of a switch 8) shown in FIGURES l, 2 and 3, which switch is acturated through a motion transmitting cable 81 to operate an :indicator light and stop the machine.

One additional limit switch is provided to detect the failure of a part to drop out of the work holder after lbroaching, with this switch being indicated at 85 in FIG- URE 1 and including a pivotal fee'ler 86 positioned to be engaged by a part remaining in the work holding drum 21 to shift contact with the switch to stop the drive motor and operate an indicator light in the event a part remains in the drum.

The feed wheel 31 and parts Iassociated therewith are mounted on and within la housing 87 which is supported from the frame of the machine by an arm 88.

The broaching tool is shown in FIGURES 12-14 and embodies Aa generally flat blade-shaped body 90 with a 4 series of teeth 91 along one edge thereof arranged to dene a curved cutting prole with the specific form being shown as an arc of a circle. The body of the blade is shaped to have a rear edge 92 and a trailing side edge 93 arranged at an acute angle of approximately 60 and With the trailing side edge 93 being generally parallel to a face 94 of a cutting tooth. The back edge 92 of the blade body is generally parallel to a tangent of the curved cutting profile intermediate its ends. As shown, the teeth have a positive rake angle and have a form whereby the tooth is identical after sharpening, and also the location of the teeth is maintained identically relative to broach holder locating surfaces subsequently to be described.

Each of the broaching stations 23 and 24 is basically the same, with the second station being used only to provide a depth of cut in a workpiece greater than that provided by the first station.

Each of the broach holders 23 and 24 is similar, and the broach holder 23 will be described in detail. The broach holder embodies a frame 190 with a plate 101 against which the broach 94) rests, and the broach is held within the holder by a quick release mechanism embodying an arm 102 which is pivoted at 193 to a member 1G41 swivellymounted in the frame 100. The opposite end of the arm 1%2 has an open ended slot 195 which fits an undercut part of a pin 106 secured in the frame 100. The arm 102 carries a pair of threaded members 197 and 108, each of which has pressure pads 1119 which engage the opposite face of the broach body 9S. With the parts in assembled relation as shown in FIGURES 4 and 5, the turning of the members 1117 and 1&8 causes the pads to rmly engage the broach and to hold the arm 1482 in broach clamping position. When it is desired to change a broach, the members 107 and 1% are backed off, which then frees the arm 102 for rotation about the swivel 194 until the notch 105 is released from the pin 1&6 and then the arm 1&2 may be swung about the pivot 1613 to move the arm out of the way for access to the broach.

The broach in effect is held in aV slot with a bottom or left-hand side of the slot as viewed in FlGURE 4 being defined by a bar 11) carried on a base 111 which is adjustably mounted on the frame 169 by means of a'central key 1121. The adjustment of the base 111 relative to the frame 11)@ is obtained by the threaded member 113, and the position is maintained by a pair of tightening bolts 114 and 115 which pass through slots in the base 111 and attach to the frame 100. The key 112 is arranged at an angle of 15 to a radian from the axis of rotation 22 for the work holding drum 21. The thrust of the broaching action is taken by a member having a at surface to engage the side edge 93 of the broach tool, and this member can rotate to maintain its contact with the edge of the broach tool even Vthough the inclination of the broach may be varied as subsequently described. The member 110 against which the rear edge 92 of the broach engages, in addition to being movable with the holder base 111, is mounted for pivotal movement about a pivot pin which is on a radial line of the work holding drum axis 22 which also passes through the last tooth 91 of the broach tool` This angular adjustment permits tilting of the tool to determine the rise per tooth and with the relation along the radial line, permits this While maintaining the setting of the last tooth for final depth of cut. The angular adjustment of the member 110 is accomplished by rotation of a pin 126 having an eccentric surface 127 engageable with the member 110. The adjustment movement is permitted by loosening of a tightening bolt 128 passing through an oversize opening in the member 110, which is of a size to avoid any interference with the angular adjustment, and when the tightening bolt is tightened the member 11i) is held in an adjusted position.

As stated previously, the broach holder at broach station 24 is the same as the holder at station 23 and similar reference numerals have been applied thereto.

We claim:

1. In a rotary broaching machine, a broach having a blade-shaped body with a plurality of teeth arranged to define a curved cutting profile as an arc of a cricle, said body having a back edge generally parallel to a tangent of said circle and a side edge at an angle of approximately 60 degrees t-o the back edge and generally parallel to the faces of the cutting teeth.

2. In a rotary broaching machine, a broach having a blade-shaped body with a plurality of teeth arranged to dene a Curved cutting profile as an arc of a circle, said body having a back edge generally parallel to a tangent of said circle and a side edge at an acute angle to the back edge and generally parallel to the faces of the cutting teeth.

3. A broach having a at blade-shaped body with a plurality of teeth along one edge thereof with each tooth having a face extending inwardly from the cutting edge of the tooth and delining a positive rake angle with respect to a workpiece path, said body having a back edge opposite to said one edge, a trailing side edge connecting said one edge and the back edge extending at an acute angle to said back edge and generally parallel to the face of the tooth adjacent said side edge whereby the tooth form and location remains in a constant relation to said side edge after each sharpening of the broach,

4. A broach as defined in claim 3 in which is a remaining side edge of said body is at a distance from the nearest tooth to provide suicient body material for repeated sharpenings as said nearest tooth progressively approaches said back edge.

5. A broach having a generally planar body of a trapezoidal conliguration with generally parallel side edges one of which trails the other with respect to a workpiece path, a back edge extending between said side edges and a row of cutting teeth extending along the remaining edge, the trailing one of said side edges and the back edge intersecting at an acute angle to each other with the resultant force from cutting directed generally toward said intersection, one of said teeth adjacent said one side edge having a face extending inwardly from said remaining edge generally parallel to said trailing one side edge and defining a positive rake angle with respect to said workpiece path, whereby said one tooth remains in known relation to said intersection after repeated sharpening of the broach.

6. A broach having a generally planar body of a trapezoidal configuration with generally parallel side edges, a back edge extending between said side edges and a row of cutting teeth extending along the remaining edge, one of said side edges and the back edge intersecting at an acute angle to each other with the resultant force from cutting directed generally toward said intersection, one of said teeth adjacent said one side edge having a face extending generally parallel to said one side edge whereby said one tooth remains in known relation to said intersection after repeated sharpening of the broach, each of said cutting teeth lying on an arc of a circle with said back edge extending generally parallel to a line tangent with a tooth located generally midway between the ends of said row of teeth.

References Cited by the Examiner UNITED STATES PATENTS 2,392,481 1/1946 Kaplan et al. 2995.1 2,468,745 5/ 1949 Garand 29-95.1 2,502,711 4/1950 Evans 29-95.1 X 2,508,534 5/1950 Paxson 90S6 FOREIGN PATENTS 119,748 5/ 1901 Germany. 489,787 9/ 1930 Germany.

WILLIAM W. DYER, JR. Primary Examiner.

LEONIDAS VLACHOS, Examiner. 

1. IN A ROTARY BROACHING MACHINE, A BROACH HAVING A BLADE-SHAPED BODY WITH A PLURALITY OF TEETH ARRANGED TO DEFINE A CURVED CUTTING PROFILE AS AN ARC OF A CIRCLE, SAID BODY HAVING A BACK EDGE GENERALLY PARALLEL TO A TANGENT OF SAID CIRCLE AND A SIDE EDGE AT AN ANGLE OF APPROXIMATELY 60 DEGREES TO THE BACK EDGE AND GENERALLY PARALLEL TO THE FACES OF THE CUTTING TEETH. 